Improvement in steam-engines



UNITED STATES JOHN M. COOPER, OF PITTSBURG, PENNSYLVANIA.

IMPROVEMENT IN STEAM-ENGINES.

Speciiication forming part of Letters Patent N o. 118,692, datedSeptember 5, 1871.

To all whom t may concern:

Beit known that I, J OHN M. COOPER, of Pittsburg, in the county ofAllegheny and State of Pennsylvania, have invented a new and usefulImprovement in Steam-Engines; and I do hereby declare the following tobe a full, clear, and exact description thereof, reference being had tothe accompanying drawing making a part of this speciiication, in which-Figure 1 is a longitudinal section of a steamcylinder and devicesconnected therewith. Fig. 2 is a cross-section through .t x, Fig. l; andFig. 3 is an enlarged sectional view of the check-valve and ports.

Like letters of reference indicate like parts in each.

My invention relates to the construction and arrangement of secondaryports and valves in connection with a steam-en gine cylinder and piston,and, while applicable to different styles of en gines,it is especiallyuseful in p umping-engines, particularly where the resistance is great,either from the large amount of water to be raised or from theconsiderable height to which the water is to be thrown, or from bothcauses combined. Direct acting engines are commonly used for suchpurposes, and one serious difticulty, which in such use is encounteredin engines of the ordinary construction, arises from the fact that thewater-valves have to operate in a medium which offers considerableresistance to their motions. The object of my invention is to secure inthe piston, at the beginning of each stroke, a motion which shall beuniformly accelerated, and, at the end of each stroke, a motion whichshall be uniformly retarded, in order that the water-valves may open andclose gradually and without strain or jar; and to this end the nature ofmy invention consists, rst, in combining with a cushioningsteam-cylinder and piston a secondary steamport leading from at or nearthe position of the piston at the extreme end of its stroke back to theexhaust-port, in which secondary port an adjustable throttle-valve isarranged; and, second, in combining a secondary steam-port andcheckvalve with a cushioning steam-cylinder, piston, and throttle.

'I o enable others skilled in the art to make and use my improvement, Iwill proceed to describe its construction and mode of operation.

The steam-cylinder a has a piston, b, and pistonstem b, of the usual orany known construction. rlhe steam-chest a contains two pistons, c c,one on each endof the stem c, which stem carries and operates theslide-valve d. The pistons e c are packed so as to operate closely inthe steam-chest a', and receive their motions so as to give therequisite throw to the valve d by a pair of slidevalves, which, providedwith suitable ports, operate in a valve-box on the side of thesteam-chest a',- or the pistons c c may be operated by aknocker, f,which is attached to the piston-stem b', and which moves the valve-stemc', thereby throwing the valves. In the latter case the ports shouldcross, or other mode be adopted by which the throw of the pistons c oshall be in the reverse direction to that of the piston b. Such devicesare well known, and need not be further described. rEhe main cylinder ahas the usual steam and eX- haust-ports g gf, which ports g g open intothe cylinder c at a little distance from the end of the cylinder, sothat the piston b, after covering either port g g as it moves toward theend of its stroke, will cushion at such end on the steam so coniined inthe cylinder, and which is known as dead or spent steam. The result willbe that the piston b will be checked up gradually at the end of itsstroke. In order now that the piston b, as it cushions on the steamafter covering the port g through which the steam was being exhaust-ed,

may stop more slowly, or with a motion more uniformly retarded, I make asmall secondary port, e, opening into the cylinder at or near the pointoccupied by the front face of the piston b at the extreme end of itsstroke, or at any suitable point forward thereof, and leading back intothe exhaust g. At any suitable or convenient point I arrange in thisport e a throttle-valve, fi, of any known construction, eitherself-acting or adjustable by a screw, t', or otherwise, at pleasure. Thesize of this port e, or of the opening through or under the throttle t',is so small that only a portion ofthe steam in the cylinder a on whichthe piston b is cushioning can escape into the eX- haust after thepiston b has covered the exhaust and before it has reached the extremeend of its stroke; and the size of the throttle-openin g can beregulated at pleasure, so as to regulate the resistance offered by thesteam in cushioning the piston b, and thus cause the piston to move tothe end of its stroke with a more uniform and slower retardation. But ator about the time the piston b reaches the end of its stroke theshifting of the valves (l opens the opposite exhaust and supplies theport g with live steam, which, however, cannot enter the cylinderthrough the main port until the piston bl has uncovered the port.

To start the piston b on its return stroke, and to secure a uniformlyaccelerated motion in the piston b from the very beginning of itsstroke, I allow the live steam to iiow through the port e and underthrottle i, from the port g, into the cylinder in front of the piston.But as this will not always give the amount of pressure desired, I openanother small port, n, from the port g to the cylinder in front of thepiston b, and arrange .Y in it a check-valve, n', soA that it will allowthe live steam to enter the cylinder, but will not allow the escape ofsteam through it while the piston is cushioning. This check-valve n',made of any known form, may also be made adjustable by a screw-socket,o, or in other known way, so as to enlarge or lessen the size of theaperture through which the steam passes into the cylinder. By the use ofthe two ports e and n the live steam can be fed into the cylinderforward of the piston, so as to exert any desirable force from theinstant the piston starts on its return stroke until it uncovers theport g. A uniformly accelerated motion will thus be imparted to it, thewater-valves will be brought down gradually7 and all unnecessary strainand jar avoided.

Such secondary ports and valves I arrange at both ends of the cylinder,the construction and arrangement at the opposite end being the same asthat sho'wn and described.

I do not' claim, broadly, a cushioning-piston and cylinder, nor acheck-valve arranged in a secondary port in connection with such apiston and cylinder, as I am aware both are old.

What I claim as my invention, and desire to Y secure by Letters Patent,is-

The throttle i and check-valve n', arranged respectively in thesecondary ports e and n, in combination with a cushioning-cylinder andpiston, substantially as set forth.

In testimony whereof I, the said JOHN M. COOP- ER, have hereunto set myhand.

JOHN M. COOPER.

Witnesses:

A. S. NICHOLSON, G. H. CHRISTY.

